Submarine missing in south Atlantic

Whipping winds and six-metre waves in the south Atlantic continue to hinder a frantic search for an Argentine submarine with 44 crew members on board, the navy says.

Authorities were readying a mission to comb the sea floor for signs of the missing vessel on Saturday.

The German-built AR San Juan submarine last reported its location 432km off Argentina's southern Atlantic coast early on Wednesday, prompting authorities to launch an emergency search-and-rescue operation on Friday.

But a storm with powerful winds and waves six meters high continued to disrupt visibility and efforts to explore Argentine's southern sea, navy spokesman Enrique Balbi told reporters.

Nevertheless, authorities were doubling down on search efforts above and below the water's surface and were readying an operation to comb the bottom of the ocean, said Gabriel Gonzalez, who heads the navy's base in the port of Mar del Plata.

The submarine had been headed to Mar del Plata from the city of Ushuaia.

"The underwater search is obviously much more complicated than the search at the surface because it requires a combination of high-tech tools," Mr Gonzalez told a news conference.

Poor conditions were expected to hold until Sunday afternoon, said a person in the navy.

Carlos Zavalla, a navy commander, urged the loved ones of crew members not to give up hope.

"So far, the only concrete thing is the lack of communication," he said on local TV channel A24. "That's all."

Messages of support have poured in from abroad. Pope Francis, a native Argentine, is praying "fervently" for crew members to return to their families soon, his office said on Saturday.

Argentina accepted an offer from the US for a NASA P-3 explorer aircraft that had been stationed in Ushuaia. A Hercules C-130 from the Argentine Air Force has also been flying over the area.

The navy has said it believed an electrical outage on the submarine may have caused its communication problems. Navy protocol calls for submarines to surface when communication is lost.